Writes a networkx.DiGraph to two shapefiles, edges and nodes.
Nodes and edges are expected to have a Well Known Binary (Wkb) or
Well Known Text (Wkt) key in order to generate geometries. Also
acceptable are nodes with a numeric tuple key (x,y).

“The Esri Shapefile or simply a shapefile is a popular geospatial vector
data format for geographic information systems software [1].”